运用同调代数理论,给出模的余纯平坦维数l.c.fd_R(M)与环的余纯平坦(弱)整体维数l.cf D(R)的换环定理,即对任意环R和任意左R-模M,都有l.c.fd_(R[x])(M[x])=l.c.fd_R(M)和l.cfD(R[x])=l.cf D(R)+1成立。同时证明:如果整环R满足cfD(R)≤1,则R是凝聚的。
In terms of the homological algebra theory, the change theorem of rings on the copure flat di- mensions l. c. fdR(M) of module M and the copure flat global dimensions l. cfD(R) of ring R is given. That is, for any ring R and any left R-module M, l. c. fdR[x] (Mix]) =l. c. fdR(M), and l. cfD(R[x] ) = l. cfD (R) + 1 hold. Furthermore, it is shown that a domain R with cfD (R) ≤ 1 is coherent.